Electrolytic production of gelatinous titanium hydrate nuclei



vision of a method of'removing such monovalent Patented Dec. 12, 1950 UNITED STATES PATENT" GFFICE 2,533,208; ELECTROLYTIC PRoDUcT lbfi qF- GEfiA l INOUSE; TITANIUM HYDRA'DE NUCIEEIJ Benjamin Wilson Allan and Frank; OlIthmmefy; Baltimore, Mdi:

No Drawing! ApplicatiomAugflsV-22;1944; Serial No. 550,672.

6 Claims.

This inventiom rel-atesfito thexproduction of ti- (Cl. ant-1st):

tanium oxide pigments and has. special. referv ence to, novel' purification of; seedI for: use in the hydrolyseso of" hydrolyzable titanium, salt" dis.- persion, the hydrolysate, off which yields. rutile titanium dioxide. pigment on calcination;

In the hydrolyses of titaniumsaltr solutions} particularly titanium sulfatersolutions, it is'agenerally, desirable thatfltheise'ed' nuclei prepared from dispersions containing monovalent anionsv be freed of such monovalent anions priorto their, useas seeds Because. of the corrosiveac-tion-iof" such a solution on ladihydrolysisl,equipment; it is importantto remove; the, monob'a'sicl acid by; some simple and economical' means. For such removal ofextraneous; anions, laborious coagu-, lation, filtration and washing, has been resorted; tohereofore.

Among the objects of 'this'invention is the proanions from the titanium hydratelnuclei that is more eificient, cheaper and less laborious than the methods heretofore employfed and does not impair the efficacy of "thei nuclei 'o'fseed.

vision of an electrolytic; process-- of? removing monovalent anions from titanium hydrate nuclei prepared by a variety of methods and materials.

Other, further and more specific objects of this invention" willbecome readily apparent to 'per- :1

sons skilled in the art from a consideration ofithe followingdescription.

Welhave; found by electrolyzing; dispersions-50f: nuclear titanium hydrate; preparedzbya' wid varietyqof waysand from alwide varietyrof;mas: terials, that effective and efl'lci'ent removal of undesirable, extraneous anionss'is'i accomplished in a cheaper and easier manner than by; the: processes formerly practiced. We have; also found that the values ofthenucleartitaniumhydrate as seed in hydrolysis =arecnothirnpaireds Our invention is applicable to various: types of cured seed, such as thoseuprep'ared. from=peptized sols, solutions,- dilute seedsglet'cz whether or not stabilizers are present-duringcuringi as will be seen from the following exainple'si For this electrolysis, there ar'e ein pl'oyed eiec trodes of platinum,metaldreei-graphite; or other suitable material which are immersedfiso thata direct vcurrent :may be passed: through the seed suspension with the mono-basic acid aicting aslthel electrolyte. The solution is -agitatedlirapidly as: electrolysis proceeds"- and any" deposition of co agulated seed nuclei is removed' -from the eie'c trodes-1 by frequent scraping or brushinge- The the HCl.

' dilute HCl solution;

' was' raisedltoi, ass-9 sec: in; 15,. minutes; nm

2.1 current; which may be supplied by'a low voltage, high amperage; direct-current generator, liberatesrh-ydrogemand chlorine. at thecathodeand: anode respectively,,asadecomposition products of" The electrolyticrmethod admits of collyection a-tt the?electrodes=- of the hydrogen and chlorinegases, if-desired;

Generally: my semi permeab1e== membrane is used to separate the"- electi'odes-i' However} if it? is desired to reduce a portion- 0f the dispersed" T102 to the trivalent condition}-a c1ose fitting membrane is placed arou-nd the anode, allowing sufiicient space between it' and the anode to contain a si'iiall" mound of el'cti"olyi'ie; such as When suificient reduction has tahen place-ethe membrane may; be, removed and thei electrolysis l completed without am membrane.

EXAMPLE I Seed from titanium tetrachloride A solution ofiti tanium tetrachloride containing 102 g./l. TiOa'ndilQfi gJllHCJU-Was treated with 170 g./l. NazG3 to= precipitate titanium ortho A further object :of this invention is the prohydrate at Thyhydratea was filtered and :washed substantially. chloride free andtpeptizfedgwithfllfilgs:HCI'fper'llmgITiOi, eoneigliie stabilizen was added"so-that12%. bone" glue." present on the ba'sisof theTiQi andthe diSper-- siondiluted tov 6 0 g./'1., TiOa, Trier-tempera e"- tai-nediin athat ra'nige; for} 10 minutes-to develop the desired nucIeatin'gprDpertiS aridtfieh icooled quickly-to 3o"fC.i

- cin'i' ofthef stable, opalseentj curfed" seed dis ersion was: electrolyzediwith' carbon elec"- trodes having cneisquare urch efifctive surfaces"; The, electrodes" were immersed; one? inch apart] in the; seed dispersion, which wa'sico'oled by a; water coil'i. TneeIectroIysi's Wasat'c'ci1'staht"tnii= peraturejofi 30? CC, and continued tuntiI the sol "1 hadfbecomegelatimzedl Tame: shows" the; variations in: vo'ltag'e';-atrr'- pares, concentration: of? H01 and concentration" of s'I'iO'i':

The final mol ratio of I-ICl/TiOz was found to be 0.17.

The small residual amount of HCl adsorbed to the TiOz seed nuclei, as in thegel product of the electrolysis, was found to have very little corrosive action on lead.

EXAMPLE II Seed from titanyl sulfate A solution of titanyl sulfate containing '75 g./l. TiOz and 177 g./l. H2804. was treated with 1'70 g./l. NazCOs to precipitate titanium ortho hy drate at 7.5 pH. The hydrate was filtered and washed substantially sulfate free, peptized with 0.6 g. I-lCl per 1.0 g. TiOz, treated with 2% citric acid as stabilizer on the basis of the T102, and diluted to 60 g./l. T102. The dispersion wa found to contain sulfate equivalent to 0.21% H2804 on the basis of TiOz. The seed was cured and electrolyzed as in Example I, to low HCl/TiOz ratio.

EXAMPLE III titanium tetrachloride without any stabilizer Titanium tetrachloride was diluted to g./l. T102, heated in minutes to 85-95 0., and cured in that range of temperature for 10 minutes to develop the desired nucleating properties,

Dilute seed from then cooled quickly to C. and electrolyzed to low ratio HCl/TiOz as in Example I.

EXAMPLE IV Seed from plant liquor containing g./l. T102 and 9.2 g./Z. Fe

The following ordinary plant hydrolysis liquor,

made from ilmenite ore, was carefully clarified and used to make a seed containing iron:

Total T102 =260 g./l. Reduced T102 =9.1 g./l. Fe :41 g./l.

Total H2304 =625 g./1. Active H2SO4 =553 g./l. Acid Factor =1.74

Reduced T102 is the sulfate of titanium wherein a the titanium is in the trivalent condition,

The solution was treated with 170 g./l. NazCOs to precipitate titanium ortho hydrate at 7.5 pH. The hydrate was filtered, washed until the filtrate showed no precipitate with barium chloride, and peptized with 0.6 g. HCl per 1.0 g. TiOz. The dispersion was found to contain 9.2 g./l. Fe. Sufficient hydrochloric acid was added to just form ferrous chloride with the iron. The dispersion was reduced electrolytically using graphite electrodes, with the anode separated from the seed dispersion by a porous membrane containin dilute I-ICl, until approximately 1 g./l. TiO2 was present as titanous chloride. Bone glue was added to the extent of 0.5% on the base of the TiOz, and the sol was diluted to 60 g./l. T102. The temperature was raised in 15 minutes to -95 C. and maintained in that range of temperature for 10 minutes in order to develop the desired nucleating properties, and then cooled quickly to 30 C.

One liter of the seed dispersion was electrolyzed with graphite electrodes, each having 20 square inches effective surface. The electrodes were immersed, one inch apart, in the seed dispersion,

duce undesirable foreign matter.

which was cooled by a water coil. The temperature was maintained at 30 C., and electrolysis was continued to complete gelation of the sol.

Table II shows the progress of the electrolysis.

TABLE 11 Time H01 T102 min. Amps g./l. g./l.

' The final mol ratio of HCl/TiOz Was found to be 0.17.

EXAMPLE V Seed by metathesis A solution of titanyl sulfate containing 270 g./l. T102 and 507 g./l. H2804 was treated with a thick water slurry of CaCOs suificient to reduce the soluble sulfate content to 0.81 g. H2804 per 1.0 g. TiO2 (equivalent to 0.6 g. HCl per 1.0 g. TiOz). The insoluble CaSOr was removed by filtration. Barium chloride solution, the chemical equivalent of the remaining sulfate, was added to the filtrate. The resulting BaSO4 precipitate was removed by filtration.

The clear filtrate was treated with dilute bone glue equivalent to 2% glue on the basis of TiO2. The concentration was adjusted to 60 g./l. TiOz,

the seed cured 10 minutes at 85-95 C., cooled to 30 C., and electrolyzed to low HC1/Ti02 ratio by means of platinum electrodes.

Table III shows the progress of the electrolysis.

TABLE III Time HG], TiOz min. AmPS- g./l 1.

o 5 so. 1 60. o 30 5 28.0 60. 4 e0 5 20. 4 61. 0 9o 5 14. 2 e1. 5 120 5 (i. 9 G2. 2

5 fecting a lower cost of installation.

3. While other methods have been found to entail TiOz losses up to 20% of the initial weight TiOz treated, in our process there is practically no TiOz loss.

4. The use of high-grade electrodes, such as graphite, platinum, etc. avoids contamination of the product. In the methods heretofore employed, the addition of various reagents as well as the salts of the wash water served to intro- Such impurities have been found harmful especially when dealing with colloidal systems such as those containing nucleating sols.

5. When operating with seeds from plant liquor containing iron, which must be reduced by some means prior to curing of the seed in order to prevent the formation of colloidal ferric oxide, such reduction is accomplished during the electrolysis by merely employin a semi-permeable membrane as heretofore described. In prior proc esses, the reduction of the iron is accomplished by adding a metal to effect chemical reduction of the titanic sulfate to titanous sulfate and to reduce the iron, thus introducing extraneous ions.

In the preparation of the above stable seed dispersions, ratios of 0.4 to 0.9 g. HCl per 1.0 g. TiOz are usable, the ratio of 0.6 g. HCl per 1.0 g. T102 being preferred.

The expression cure and its derivatives are used to denote the conversion by heating of orthotitanic acid sols prepared with monobasic acid, which sols are soluble in dilute acids, as well as other compounds of titanium and monobasic acid, which compounds are soluble in dilute acids, into sols of metatitanic acid which are insoluble in dilute acids.

The term stabilizer and its derivatives are used to denote the prevention of secondary agglomeration of the cured seed after the primary growth thereof has been arrested by cooling, with consequent impartation to the dispersed titanium hydrate seed of the property of maintaining practically its entire activity, potency and efficiency as a seed for prolonged period of time after stabilization, as distinguished from the relatively short period of efiectiveness of the dispersed titanium hydrate seed before stabilization. It is the specific phenomenon of preventing the submicroscopic crystal seeds from growing together into microscopic and macroscopic crystal seeds.

The present inventionis not limited to the specific details set forth in the foregoing examples which should be construed as illustrative and not by way of limitation, and in view of the enumerous modifications which may be effected therein without departing from the spirit and scope of this invention, it is desired that only such limitations be imposed as are indicated in the appended claims.

We claim as our invention:

1. In a process of making a seed for the hydrolysis of hydrolyzable titanium salt dispersions, forming titanium hydrate nuclei by heating and curing a dispersion of a member of the class consisting of the hydrochloric acid salts of titanium and the orthohydrate of titanium peptized with HCl, cooling and then removing HCl from the nuclei and effecting gelatinization of said nuclei by electrolyzing a dispersion of the nuclei in aqueous HCl whereby hydrogen gas is evolved at the cathode and chlorine gas is evolved at the anode, the electrolysis being conducted with anode insoluble in the electrolyte.

2. In a process of making a stabilized seed for the hydrolysis of hydrolyzable titanium salt dispersions, forming stabilized titanium hydrate nuclei by heating and curing a dispersion of a memher of the class consisting of the hydrochloric acid salts of titanium and the orthohydrate of titanium peptized with 1101, a stabilizer having been added to said dispersion before curing, cooling and then removin HCl from the nuclei and effecting gelatinization of said nuclei by electrolyzing a dispersion of the nuclei in aqueous HCl whereby hydrogen gas is evolved at the cathode and chlorine gas is evolved at the anode, the electrolysis being conducted with anode insoluble in the electrolyte.

3. In a process of making a seed for the hydrolysis of hydrolyzable titanium salt dispersions, forming titanium hydrate nuclei by heating and curing a dispersion of a hydrochloric acid salt of titanium, cooling and then removing HCl from I the nuclei and efiecting gelatinization of said nuclei by electrolyzing a dispersion of the nuclei in aqueous HCl whereby hydrogen gas is evolved at the cathode and chlorine gas is evolved at the anode, the electrolysis being conducted with an ode insoluble in the electrolyte.

4. In a process of making a seed for the hydrolysis of hydrolyzable titanium salt dispersions, forming titanium hydrate nuclei by heating and curing a dispersion of orthohydrate of titanium peptized with HCl, cooling and then removing HCl from the nuclei and eifecting gelatinization of said nuclei by electrolyzing a dispersion of the nuclei in aqueous I-ICl whereby hydrogen gas is evolved at the cathode and chlorine as is evolved at the anode, the electrolysis being conducted with anode insoluble in the electrolyte.

5. The process claimed in claim 1, wherein the electrolysis is effected in a two-compartment cell.

6. The process claimed in claim 1, wherein the electrolysis is effected in a two-compartment cell while the electrolyte is agitated.

' BENJAMIN WILSON ALLAN.

FRANK O. RUMMERY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1 923,745 Whitney June 1, 1909 1,132,394 Schwerin Mar. 16, 1915 1,216,371 Schwerin Feb. 20, 1917 1,235,638 Barton Aug. 7, 1917 1,326,105 Schwerin Dec. 23, 1919 1,746,542 Low Feb. 11, 1930 1,766,592 Blumenfeld June 24, 1930 1,878,235 Gortner et al Sept. 20, 1932 2,017,049 Jones Oct. 15, 1935 2,073,621 Blaney Mar. 16, 1937 2,285,485 .Barksdale et a1 June 9, 1942 2,342,483 Olson Feb. 22, 1944 I FOREIGN PATENTS Number Country Date 533,227 Great Britain Feb. 10, 1941 OTHER REFERENCES Komagata: Transactions of Electrochemical Society, vol. 73 (1938) pp. 511-522. 

1. IN A PROCESS OF MAKING A SEED FOR THE HYDROLYSIS OF HYDROLYZABLE TITANIUM SALT DISPERSIONS, FORMING TITANIUM HYDRATE NUCLEI BY HEATING AND CURING A DISPERSION OF A MEMBER OF THE CLASS CONSISTING OF THE HYDROCHLORIC ACID SALTS OF TITANIUM AND THE ORTHOHYDRATE OF TITANIUM PEPTIZED WITH HC1, COOLING AND THEN REMOVING HC1 FROM THE NUCLEI AND EFFECTING GELATINIZATION OF SAID NUCLEI BY ELECTROLYZING A DISPERSION OF THE NUCLEI IN AQUEOUS HC1 WHEREBY HYDROGEN GAS IS EVOLVED AT THE CATHODE AND CHLORINE GAS IS EVOLVED AT THE ANODE, THE ELECTROLYSIS BEING CONDUCTED WITH ANODE INSOLUBLE IN THE ELECROLYTE. 